RM250 wont hit power ban

[ihavenousername]

my mate just bought a 98 rm250 and it wont rev at all. it idles fine and runs fine in low RPM until its just about to hit power ban and then it just splutters and wont accelerate. this will happen in every gear.

what could cause this? carby and air filter are clean. we think it could be spark related or mabi reed valve.

we're running a B8es plug which isn't recommended but the bike was running with one in it while the the previous owner had.

 

[Isobareng]

This is a common problem with 2 strokes about that age check for a clog of carbon in the exhaust system first. you can also for just a minute or so start the bike with the exhaust off and see if the sputter disappears. if that isn't it look for a place along your ignition wires that may be compromised with some resistance to ground. often around the steering/ tank area.

 

[allthingsdirt]

Just a shot in the dark.... check to make sure the power valve is working properly. Also, checking the reeds is easy enough to do. Pull 'em out and make sure they aren't worn out or chipped.

 

[Rotorranch]

Reduced fuel flow from a plugged petcock?

Rotor

 

[fatboyslim]

I'm betting its a carboned up powervalve because if it is sputtering at high rpm then the exhaust flange in the cylinder isn't opening like it's supposed to at high rpm, hence the sputter effect.

 

[a454elk]

Easy to see if the power valve is working, pull the PV cover on the right side and see if it can move. If the PV is the problem, make sure to check that the lower end of the actuator bar is connected on the engine side below, as well as checking if the valve is stuck. I had the powerband problem with my 01 zook but it didn't sputter at higher rpms, it just never opened the valve so you never got the "hit". It could be a dirty carb, fuel flow. Check the carb and all jets. Let us know what you find out so we can store it in the back of our dirt minds. ;)

 

[helio lucas]

i´m not sure what means splutter... but here is my guess:

a stuck exhaust valve in closed position makes the bike run flat in high rpm, not splutter... in open position maybe, but only in low rpm...

a faulty ignition could make the hit smoother or harder, but normaly not splutter with less hit and normal low rpm...

a clogged exhaust also makes the power flat at high rpm, once again, not splutter...

a bad top end could do some of the simptoms discribed, but normally is worse in loe rpm...

my bet is a bad spark plug or a dirty filter (or carburator)...